Electrical precipitator



y 29, 1951 H. A. WINTERMUTE ELECTRICAL PRECIPITATOR 7 Sheets-Sheet 1 Filed Sept. 24, 1946 a 3 W m 0 m r mm 2 m m w d M J 4 4 4 H a I 1 Jw Av m. I! 2 "w 1 rrrou [m u I -5 6 u: f 7 4 a 4 N 4 y 1951 H. A. WINTERMUTE ELECTRICAL PRECIPITATOR 7 Sheets-Sheet 3 Filed Sept. 24, 1946 INVENTOR. HarryA. Wz'marmule.

M y 1 H. A. WINTERMUTE 2,555,216

ELECTRICAL PRECIPITATOR Filed Sept. 24, 1946 Sheets-Sheet 4 IN V EN TOR.

May 29, 1951 H. A. WINTERMUTE 2,555,216

' ELECTRICAL PRECIPITATOR Filed Sept. 24, 1946 1' Sheets-Sheet 5 0 00000 00000 00000 00000 000000000000000000000 000000000000000000000 000000000000000000000 0 00000 00000 00.000 00000 0 00 0 00 00000 00000 00000 000000000000000000000 0 00000 00000 0000000000 0 00000 00000 00000 00000 W W 7- so 28 J EC 'r/o/v 12-12 INVENTOR. HarryAWmfermuze.

May 29, 1951 H. A. WINTERMUTE ELECTRICAL PRECIPITATOR '7 Sheets-Sheet 6 Filed Sept. 24, 1946 Harry 1 N VEN TOR. A Wmzermafe BY 5M T 5W4 y 9, 1951 H. A. WINTERMUTE 2,555,216

ELECTRICAL PRECIPITATOR Filed Sept. 24, 1946 7 Sheets-Sheet 7 INVENTOR.

Patented May 29, 1951 ELECTRICAL PRECIPITATOR Harry A. Wintermute, Plainfield, N. J., assignor to Research Corporation, New York, N. Y., a corporation of New York Application September 24, 1946, Serial No. 698,978

This invention relates to electrical precipitators and more particularly to electrical precipitators having means providing for uniform gas flow therethrough and having liquid-flushed collecting electrodes.

An object of the inventionis to provide an electrical precipitator, preferably but not necessarily a precipitator of the vertical-flow type, wherein the extended surface electrodes extend in the vertical direction and wherein means is provided for directing a spray of flushing liquid over the surfaces of the electrodes including liquid distributors for catching the spray and directing the intercepted liquid over the surfaces of the extended surface electrodes and wherein means is provided for establishing substantially uniform gas flow past the extended surface electrodes.

Another object is to provide an improved vertical-flow electrical precipitator of the type having a charging section wherein gas-borne par ticles are given an electrical charge and in part precipitated and a collecting or precipitating section wherein the charged particles are substantially completely removed from the gas stream. In such a precipitator, extended surface electrodes of novel construction and particularly adapted to be flushed free from precipitated matter in a very efiicient manner have been provided. The novel extended surface electrodes specifically described herein are simply, easily and cheaply constructed in a preferred embodiment from perforate web material such as Woven wire screen.

Typically, an electrical precipitator in accordance with the invention includes a casing, vertically extending extended surface electrodes defining a plurality of gas passages openat the tops thereof, complementary precipitating electrodes in each of said gas passages, liquid'spray means positioned to direct a spray of flushing liquid above said extended surface electrodes, a plenum chamber in said casing on the upstream side of said passages, and gas inlet means opening into said plenum chamber. there is provided means for establishing substantially uniform gas flow through said gas passages comprising a perforate plate member extending transversely of said casing between said plenum chamber and said gas passages and a plurality of web members defining other gas passages extending from said perforate plate rectilinearly towards said first gas passages, and liquid distributors comprising. perforate web members sloping downwardly over thetop openingsof said first gas passages into substantialcontact with In such a precipitator,

12 Claims. (01. 183 -7) "said extended surface electrodes whereby to intercept liquid spray from said spray means and direct the flow of intercepted liquid to the surfaces of said extended surface electrodes.

The invention will be more particularly described and other of its aims, objects and advantages will be in part apparent and in part pointed out in the following detailed description taken in connection with the accompanying drawings in which:

Fig. l is a vertical sectional view taken through an up-draft vertical-flow precipitator embodying the principles of the invention;

Fig. 2 is a similar view of a down-draft electrical precipitator constructed in accordance with the invention;

Fig. 3 is a fragmentary plan view of one form of extended surface electrode structure-with the liquid distributing members removed;

Fig. 4 is a development in detail of a clip used in assembling the electrode structure of Fig. 3;

Fig. 5 is a sectional view taken along the line 5-5 of Fig. 3 showing the clip of Fig. 4 in the electrode assembly;

Figs. 6, '7 and 8 are views similar to Figs. 3, 4 and 5 respectively of another form .of extended surface electrode structure; 7

Fig. 9 is a fragmentary isometric view of an extended surface electrode structure showing a liquid distributing member in place;

Fig. 10 is a plan view of the structure shown in Fig. 9;

Fig. 11 is a sectional view taken along the line ll-ll of Fig. 10;

Fig. 12 is a sectional view taken along the line v 12-42 of Figs. 1 and 2 showing the gas flow disview showing the manner of attachment of a tributing assembly;

Fig. 13 is a side view of the assembly shown in Fig. 12;

Fig. 14 is an end view of an alternative form of electrode structure embodying modified liquid distributors 7 Figs. 15 and 16 are end views of further modifications of electrode structures;

Fig. 1'7 is an enlarged fragmentary sectional liquid distributing element to an electrode plate; Fig. 18 is an enlarged fragmentarv vertical sectional view of the upper corner of an electrical precipitator similar to the precipitator of Fig. 1 showing a modified liquid spray device; and

Fig. 19 is an enlarged detail side view of one of v the spray deflectors shown in Fig. 18.

Referring particularly to Fig. 1, the up-draft, vertical-flow, two-stage, precipitator shown has a casing 20, a gas inlet conduit 2i at the bottom, and a gas outlet conduit 22 at the top. Gas initially bearing suspended solid or liquid particulate matter, such as dust, smoke, mist and the like, is passed through the precipitator by a fan or other suitable means (not shown) in the directional sense of the arrows of Fig. 1, entering the precipitator from the inlet-2i, flowing vertically upwardly through the casing wherein it is cleaned, and leaving the apparatus in a cleaned condition by way of outlet 22.

Positioned Within the casing successively fil the direction of gas flow are a gas flow distributor23, a charging section 24, a collecting 'sectio'ri 25;.a liquid spray device 26, and a spray eliminator 21.

As best shown in Figs. 1, 12 and 13, the gas flow distributor has a perforate-plate 28 extend ing transversely across the casing to define the upper boundary of a plenum chamber 29, the side and bottom boundaries of which are delimited by the lower side .walls and'bottom'of the casing 23. Above the plate 28 there is positioned a cell-like structure, the cells of' which are open" at top and bottom and are formed by'a plurality" of web members 30' extending interlockingly across the casing. It will be observed that the web members 30" define gas passages extending from the perforate plate 28 rectilinear'ly' toward the charging section 24. V

The charging section 24 has a set ofco'mplementary discharge electrodes 3| and extended surface electrodes 32. The extended surface electrodes, shown more or less diagrammatically in Fig. l, are shown in detail'in Figs. 9 through 1 1 and their preferred method of assembly into a complete electrode structure isshown in Figs. 3' through 5.

Referring to Figs. 9 through 11, the extended surface electrode assembly 32 is formed largely from perforate web material, specifically woven wire screen. The extended electrode surfaces proper 33 are of substantial vertical extent and are arranged in cellular fashion to'provide a plurality of contiguous, vertically extendingv gas passages 34 having a square cross section; It will be undertood that adischarge electrode 3| projects centrally upwardly into each of the gas passages, as indicated in Fig. 1.

Each of the top openings of the gas-passages 34 is capped by a liquid distributing member 35, which, in the modification shown in Figs. 9 through 11, takes the form of an equilateral pyramidal cover inserted a short distance withinthe top of the gas passage and attached totlie electrode members by inweaving the endsof the wires depending from the covers 35 with the wire fabric of the electrodes proper, as shown in Fig. 11 along the line of contact 36. It will be understood that other methods of attachment may be employed to secure the caps'to the elec-- trodes proper; for example, the caps may be soldered to the extended surface electrodes; Although it is preferred that the bottoms of the caps contact the sides of the electrodes proper along a line somewhat below the tops of the electrodes, since liquid distribution is thereby facil-' itated, it will be understood that the line of contact may, if desired, be along the top edges of the extended surface electrodes.

As shown in Fig. 3, which is a fragmentary plan view of the extended surface electrode structure with the caps 35 removed, the structure may conveniently be assembled from lengths of wire screen appropriately formed and joined together by clips. One such length of wire screen is designated 33a and another is designated 33b. Both lengths of screen are continuous from left to right in the figure and are bent along vertical lines into the zig-zag shape shown. The two lengths of screen are joined together by means of clipstl alongcorresponding alternate vertical bends-to form th'e gas passages 34. Clips 31 are formed from sheet metal; one of them is shown developed in Fig. 4. A pair of ears 3B are disposed at each end of the clip, and, as best seeiiiii FiglbQthese ears are bent over the tops of the screen lengths'33a and 33b to secure the two-lengths together. It will be understood that theclips-extend for the full height of the screen electrodes and that the cars 38 at the bottom of the clipsare bent under the bottom edges of the screenlengths for the purpose of rendering the extended surface electrode structure sufficiently rigid.

An alternative extended surface electrode structure and its method of assembly is illustrated in Figs. 6 through 8. Here, the gas passages are hexa onal in cross section. The elecsection 24.

trode structure is formed from continuous lengths of wire screen, such as 330' and 33d, bent at angles and fastened together by clip's38 having ears 39" and 4QWhich are bent 3 (rover adjacent edges of the screen lengths, as

shown in Figs. 6 and 8'. When the electrode structure takes the alternative form, hexagonal pyramidal caps or liquid distributors (not shown) are provided and are attached to the tops of the electrodes in a manner analogous to the attachment'of the caps 35' as described with reference to Figs. Qthrough 11.

An extended surface'electrode assembly, such as either of those just described or the equivalent thereof, is positioned'in the charging section 24 of the precipitator as shown in Fig. l. The complementary discharge electrodes 3!, which project into each gas passage of the extendeds'urface electrode structure 3 2, have finewire discharge portions such as'are'indicated at 40 and 4|. The discharge electrodes 3| are supported on transverse bus bars 42' carried by insulato'is43 andinsulating' bushings 44 secured to the casing 20 in protected recesses 45 at the sideso'f the casing.

A source of high tension current (not shown) provides power to the discharge electrodes 31 through a lead 46' which passes through the insulating bushing 44 and is connected to the bus bar 42. The casing may be grounded as indicated at 41, and through the casing, the extended surface" electrode structure 32 may also be grounded.

The collecting section 25 is very similar in construction and arrangement to the charging It has. complementary precipitating electrodes 48 and collecting electrodes 49.

The precipitating electrodes aremounted similarly to the discharge electrodes 3| on transverse bus bars 50 supported by insulators 5! and insulating bushings 52 housed in recesses at the sides of the casing. A conductor 53, which passes through the bushing 52 and is connected to the bus bar 50, leads high tension current to the precipitating electrodes 48. It will be noted that precipitating electrodes 48 have no discharge'points or fine wires.

The collecting electrodes 49 are in the form of perforate web structures similar'in every respect to the extended surface electrode structures 32' hereinbefore described in connection ates-pie;

with the charging section 24, although the size and shape of the gas passages in the two sections of the precipitator may be difierent. Specifi cally, the gas passages 54 provided by the collecting electrode structure 49 may be smaller in cross section than the gas passages 34 of the charging stage to enable the use of lower potentials in the collecting stage. The gas passages d i may be formed in any appropriate sectional configuration and are capped by the liquid distributing members 55.

The liquid spray device 26 is positioned above the collecting electrode structure it to direct a spray of flushing liquid upon the liquid distributors 55 from a plurality of nozzles 56.

Spray eliminator 21 may be of any suitable or conventional design but it is specifically shown as comprising a plurality of horizontally spaced, transverse slats 51 having hooked upper and lower edges. The slats may be inclined in the direction of gas flow and function to remove entrained water from the cleaned gas stream leaving theprecipitator.

At the bottom of the plenum chamber 29, a liquid outlet 58 is provided for the discharge of liquid fro-m the sump. Conventional trap means (not shown) may be included in the liquid outlet to prevent leakage of gas therethrough while permitting discharge of liquid.

In operation of the precipitator of Fig. 1, gas to be cleaned is passed through the precipitator from bottom to top. Corona discharge is established in the charging section 24 and a high tension electrostatic field is set up in the collecting section 25 by applying suitable high potential electric currents to the complementary electrodes of these sections, as will be apparent to those skilled in the art of electrical precipitation.

Either continuous or intermittent flushing may be employed. If the flushing of the electrodes is to be carried on continuously during gas cleaning, the spray device 26 is put into operation to deliver steady sprays of flushing liquid, which may be oil, water or water-containing wetting agents or other additive materials, to the liquid distributors 55. If the conditions of operation do not require continuous flushing, the spray device may be turned on periodically or occasionally as desired, either manually or by automatic time-controlled means (not shown), for a time sufficient to effect the desired washing of the electrodes.

The spray of flushing liquid is directed downwardly upon the tops of the distributors of the collecting section, and is intercepted by these distributors. The intercepted liquid is conducted or directed by the distributors to the vertical collecting electrodes proper down which it flows in a uniform film to wash the collecting electrodes free from precipitated material.

Flushing liquiddrops from the bottoms of the collecting electrodes 49 and falls in the form of a spray upon the tops of distributors 35 of the charging stage. The distributors 35 serve to intercept and direct flushing liquid downwardly over the surfaces of extended surface electrodes .'32 from which the liquid falls to and through the gas flow distributor 23 to the sump at the bottom of the plenum chamber 29 from which the liquid is discharged through outlet 58 to waste or to means (not shown) for recirculating it to the spray device 26. 1

The gas to be cleaned passes into the plenum chamber 29 from the gas inlet 2|. Inthe plenum.

? ofthe lower horizontal threads or. strands beingupwardly through the precipitator. The perforated plate 280i the gas fiow distributor serves to creat some back pressure in the plenum chamher and to render the transverse distribution of volume flow substantially uniform. The transverse web members 30 function to straighten the flow lines of the gas stream and to direct the gas stream substantially rectilinearly toward the gas passages 34 of the charging section.

In the charging section, ionization of the gas and charging of suspended particles occurs, in general together with some precipitation of charged particles upon the extended surface electrodes 32. The gas carrying the charged particles then passes through the gas passages 54 of the collecting stage where the charged particles are largely precipitated upon the collecting electrodes 49. Cleaned gas passes upwardly through ;the spray eliminator 27, where the bulk of entrained flushing liquid is removed, and out of the 'precipitator through outlet 22 to use.

The embodiment of the invention shown in Fig. 2 is similar to that shown in Fig. 1. In Fig. 2, primed reference numerals denote parts corresponding to parts bearing like but unprimed numerals in Fig. 1.

Referring to Fig. 2, the precipitator shown is of the vertical-flow, down-draft type having a casing 25], a gas inlet pipe 2| at the top and a gas outlet pipe 22 at the bottom. Disposed within the casing successively in the direction of gas flow is a gas fiow distributor 23, a liquid spray device 26', a charging section 24', and a collecting section 25. A liquid discharge pipe 58' is provided for draining the sump of the precipitator. The upper part of the casing together with the gas flow distributor 23' defines a plenum chamber 29 into which the gas inlet pipe 2| leads gas to be cleaned. Gas flow is indicated by the arrows.

The operation of the modification of Fig. 2 is substantially the same as the operation of the device of Fig. 1 as previously described herein,

. allowances being made for the reversal of gas flow. If desired, a spray eliminator similar to the spray eliminator 27 of Fig. 1 may be employed at the gas outlet of the down-draft unit of Fig. 2.

Referring to Figs. 14 through 16, there are shown, in end elevation and somewhat diagrammatically, alternative collecting electrode structures embodying the principles of the invention.

In Fig. 14, the complementary collecting electrodes take the form of vertically eXtending solid plates 59 and 6B spaced apart horizontally. The plates are alternately oppositely charged to create electrostatic precipitating fields therebetween, as will be understood by those skilled the art to which this invention pertains.

Along the upper edge of each plate there is attached a spray intercepting and distributing panel 6 l These elements may be fabricated from woven wire screen or similar foraminous material and extend upwardly from the plates 59 and 6D atan angle of about 45 for a distance sufiicient to bring the upper free edges $2 of the screen panels slightly beyond the extended plane of the next adjacent plate, so that falling liquid spray will be substantially completely intercepted by the panels 6 land directed to and over the plates 59 and 60..

The manner of attachment of the screen panels to the plates is illustrated in Fig. 1'7. The lower edge ofthe'screen BI is frayed out, one or more acts ggisi removed from the edgeiof theifa'bricunnecessary: to provid'e afringe of loose warp' strands- B3L Alternate warp strands: 63 1 arealaid ona opposite 1 sidesof the plate 59; following :the weave .of the:

tribution. of flushing: liquid? to, both: sides of thee.

plate electrode.

The. electrode structures shown. in'i Fig; 15'; is similar to that shownzinFi'g; 14, butprovides'i for an even better distribution of flushing'liquid" between the 'two sides of: an: electrode-plate. It" may be noted that: the liquid collecting: and. distributing screen have. a vertically extending section Gti immediatelysuperjacent theplate. and anangularly diverging section 66; continu lug-upwardly from the'vertical section and overlying. the space between adjacent plates; Al'-- though, in the electrode struct'ureiof Fig. 114; the flushing liquid may-tend-to' favor the side of the. plate electrode that-is nearer the under surface of. the screen panel; this diiii'culty is' avoided in the device of Fig; 15; wherein the'vertical screen section 65 equalizes the distribution of liquid to both ides of the electrode plate.

Fig. 16 shows. a somewhat similar construction. However, instead ofutilizing solid plate electrodes, the electrodes-Bl are of wire screen or the like and have integral'spray interceptors. 68 formed by bending over-the upper sectionsofthe screen panels.

Itwill be understood that-the collecting 'elec trodestructures of Figs. 14 through 16 are suitably supported in an appropriate housing and that spray devices are provided for directing a spray of flushing liquid down upon the spray intercepting screens. It will-also be evident that the structures illustrated in these figures may be employed with either vertical or horizontal gas" flow. Moreover, by the substitution: of" fine wire discharge electrodes for'one' set of complementary plate electrodes, at single-stage'pre cipitator is provided.

The spray devices illustrated in Figs. 1 and 2' are merely exemplary and othertypes ofspray' devices may be :used without departing'from' the invention. One: such. alternative spray device which is especially advantageous is shown in: Figs. 18 and 19..

In Fig. 18, which is'a fragmentary'viewof the upper part of aprecipitator as' in Fig; 1, the parts corresponding to; like: parts. in' Fig: 11 are given the same. reference numerals. The. liquid spray device. 26 is provided. with; non-- diffusing nozzles 69 which deliver morezor'less solid jets of flushing liquid. Immediately below: each nozzle 69 thereis mounted on a horizontal? axle 15, supported by a: bracket H, carried by the pipe 26, an automatic liquid deflector 12;. The deflector i generally wedge-shaped'in:.the. portion 13 above the axle and hasiaaflaringde pending skirt portion 14 below the axle. It. is mounted. for free oscillation on; the" axle and. balanced to assume a restposition'zwitlr theuedge. of the Wedge '13 uppermost, asfshownat-Azin Fig. 18.

When the. flushing liquid is: caused to;- issue from the. nozzle 69, it. impinges: on the; upper: edge of the deflector as shown at A andidueto, slight. condition of." unbalance, immediately forces the deflector. to tLlIlIi andlassume'one. off the. limiting positions shown .atlB- or; C. Inleither or. these". positions; theiforce 'oi: thezjeteisiexertedz largely: upon the. skirt portion 14 of the d8 fiector'and' deflects a turning movement of the deflector to: carry it through its. rest position and. into its oppositelimitingposition. Theyd'e-v flector continues to oscillate" in this manner, as

long. as a jet of liquid impinges upon it. Such. oscillating action creates a uniform spray of ratherlargedrops of liquid which descends .upon' and'flushes the electrodes, as hereinbefore" described.

The spray device shown in Figs. 18 and 19' has peculiar advantages in the. present invention; Itrequire less headroom than. a spray device such as is shown in Figs; 1 and 2, thereby permitting an effective decrease in the over-all heightzof the precipitator. Additionally, thedeflector creates a minimum of fine mist, practically eliminating carrythrough of entrained flushing liquid by the gas being treated and. minimizing gas absorption in the flushing. liquid which may interfere with efiicient flushing where the flushing liquid is recirculated.

The spray intercepting devices and the extended surface electrodes proper where. made of creen advantageously are formed from wire. screening, preferably of one-eighth to threesixteenths inch mesh, or the like, but may, if

desiredjbe formed from other forarninous ma-- terial.

The spray intercepting and distributing elements may be used in some two-stage precipitators on only one set of the extended surface electrodes; for example, it may be desirable to dispense with the elements on one set of ex-' tended'surface electrodes where the cross section of the" gas passages defined by them is relatively small and/or the need for flushing the electrodes of that section is relatively minoras compared with the need for flushing the electrode of the other section.

The spray intercepting and distributing elementsmay induce a slight backpressure on the gas flowing through the gas treating zones and thereby assist in the even distribution of gas flow through the several gas passages. It will also'be een that the elements provide an effec* tive additional extended electrode area which tension: electrode, and this without increasing Such arrangement also serves to distribute the corona' discharge over a relatively wide area and thus to charge suspended particles more completely the. undesirable formation of ozone.

with' resultantliigher gas cleaning efiiciency,

The term casing is used herein in a broad sense and'isintended to include a shell; housing, or other enclosure such as a specially constructed room. for containing the, precipitator.,

equipment, and in which the equipment. may, be.

removabl'y, mounted.

Thegasflow distributing assembly shownin detailinFigs. 12.and.l3 and:electrical precipita tors. embodying the same are disclosed and:

claimed-in-my copendingapplication Serial Numrber. 107,896,,filed August 1,1949;

Electrical precipitators including theliquid spray; dGViCBSEShOWDLLiIIT detaiL-in Figs: 13*andi 19 are disclosed: and claimed: in: my copendi'ngapplication Serial Number 131,821, filed December 8, 1949.

I claim: v

1. In an electrical precipitator including a casing, vertically extending extended surface electrodes defining a plurality of gas passages open at the tops thereof, complementary precipitating electrodes in each of said gas passages, and liquid spray means positioned to direct a spray of flushing liquid above said extended surface electrodes, liquid distributors comprising perforate web members sloping downwardly over the top openings of said gas passages into direct contact with said extended surface electrodes along substantially the'entire linear extent of the tops thereof whereby to intercept liquid spray from said spray means and transfer the-flow of intercepted liquid to the surfaces of said extended surface electrodes.

2. In an electrical precipitator including a casing, vertically extending extended surface electrodes comprising perforate web members defining a plurality of gas passages open at the tops thereof, complementary precipitating electrodes in each of said gas passages, and liquid spray means positioned to direct a spray of flushing liquid above said extended surface electrodes, liquid distributors comprising perforate Web members sloping downwardly over the top openings of said gas passages into direct contact with said extended surface electrodes along substantially the entire linear extent of the tops thereof whereby to intercept liquid spray from said spray means and transfer the flow of intercepted liquid to the surfaces of said extended surface electrodes.

3. In an electrical precipitator including a casing, vertically extending extended surface electrodes comprising woven wire screen members defining a plurality of gas passages open at the tops thereof, complementary precipitating electrodes in each of said gas passages, and liquid spray means positioned to direct a spray of flushing liquid above said extended surface electrodes, liquid distributors comprising woven wire screen members sloping downwardly over the top openings of said gas passages into direct contact with said extended surface electrodes along substantially the entire linear extent of the tops thereof whereby to intercept liquid spray from said spray means and transfer the flow of intercepted liquid to the surfaces of said extended surface electrodes.

4. In an electrical precipitator including a casing, vertically extending extended surface electrodes comprising solid plate members defining a plurality of gas passages open at the tops thereof, complementary precipitating electrodes in each of said gas passages, and liquid spray means positioned to direct a spray of flushing liquid above said extended surface electrodes, liquid distributors com-prising perforate web members having a free top edge sloping.downwardly over the top openings of said gas pasinto direct contact with said extended surface electrodes along substantially the entire linear extent of the tops thereof whereby to intercept liquid spray from said spray means and transfer the flow of intercepted liquid to the surfaces of said extended surface electrodes.

5. In an electrical precipitator including a casing, vertically extending extended surface electrodes comprising mesh screen members defining a plurality of gas passages open at the top thereof, complementary precipitating electrodes '10 in each of said gas passages, and liquid spray means positioned to direct a spray of flushing li uid above said extended surface electrodes, liquid distributors comprising integral portions of the mesh screen material of the extended surface electrodes sloping downwardlyover the top openings of said gas passages whereby to intercept liquid spray from said spray means and transfer the'fiow of the intercepted liquid to the surfaces of the said extended surface electrodes.

6. In an electrical precipitator including a casing, generally vertically extending extended surface electrodes defining a plurality of passages for the flow of gas therethrough, the top edges of said electrodes being substantially horizontal, complementary precipitating electrodes in said gas passages, and liquid spraymeans positioned above said extended surface electrodes to direct a spray of flushing liquid downwardly thereover, liquid distributors comprising perforate web members positioned below said liquid spray means and sloping downwardly over thetop openings of said gas passages into direct contact with the top edges of said extended surface elec trodes along substantially the entire linear extent thereof, said perforate web members extending over the spaces between said extended surface electrodes whereby to intercept substantially all of the liquid spray from said spray means and transfer the flow of intercepted liquid to the surfaces of said extended surface electrodes.

7 A two-stage vertical draft electrical precipitator comprisin a casing; a collecting section in the upper portion of said casing comprising vertically extending extended surface electrodes defining a plurality of vertically extending gas passages, complementary non-discharge precipitating electrodes in said gas passages, liquid spray means positioned to direct a spray of flushing liquid above said extended surface electrodes, and liquid distributors comprising perforate web members sloping downwardly over the top openings of said gas passages into direct contact with said extended surface electrodes along substantially the entire linear extent of the tops thereof whereby to intercept liquid spray from said spray means and transfer the flow of intercepted liquid to the surfaces of said extended surface electrodes; a charging section in the lower portion of said casing positioned to receive the drip of flushing liquid from said collecting section, said charging section comprising vertically extending extended surface electrodes defining a plurality of vertically extending gas passages, complementary electrodes having a restricted number of discharge elements in said gas passages, and liquid distributors comprising perforate web members sloping downwardly over the top openings of said gas passages into direct contact with said extended surface electrodes along substantially the entire linear extent of the tops thereof whereby to intercept the drip of flushing liquid from said collecting section and transfer the flow of intercepted liquid to the surface of said extended surface electrodes; inlet means directing gas to be cleaned into the bottoms of the gas passages of i said charging section; outlet means for cleaned 1 1 said liquid distributors and said extended" surface electrodes comprise woven wire screen.

10. A precipitator as defined in claim- 9 wherein said extended surface electrodes are arranged to-provide gas passages of rectangular cross section and said liquid distributors comprise pyramidalcap members positioned over the gas outlet ends of said gas passages.

11". In an' electrical precipitator as defined in claim 3'; said extended surface electrodes being arranged to provide gas passages of rectangular cross-sectionand said liquid distributors comprising pyramidal c'ap" members positioned over the tops" of said gas passages.

12. In an electrical precipitator including a casing, vertically extending extended surface electrodes comprising solid plate members defining a plurality of gas passages open a the tops thereof; complementary precipitating electrodes in said gaspassages, and liquid spray means positioned to direct a spray of flushing liquid above said extended surface electrodes, liquid distributors comprising woven wire screen members sloping downwardly over the top-openings of said gas passages into direct contact with said extended surface electrodes along substanf2 tially' the entire linear extent of the tops thereof, the wire threads of the screen members alternately contacting the front and back vertical surfaces of said extended surface electrodes,

whereby to intercept liquid spray from said spray means and transfer the flow of intercepted liquid to-the front and back surfaces of said extended surface electrodes.

HARRY A-. WINTERMUTE.

REFERENCES CITED The following references are of record in the fileof this patent:

UNITED STATES PATENTS Number Name Date- 1,339;480 Schmidt May 11, 1920 1,766g4-21f Wintermute et a1. June 24-, 1930 1,968,334 Crowder et a1 July 31,1934 2,245,516 Wintermute June 10,- 1941 2 3749515 White May 1', 1945 2 4041189 Burke et al July 30, 1946 FOREIGN PATENTS Number Country Date 871,845 France Jan. 22, 1942 

